Insights

How to tackle the embodied carbon in waste

We all know that if you turn on a light or start up an excavator on site, you are going to generate carbon emissions, but have you ever considered the carbon impact of throwing away that half sheet of plasterboard, or the plastic packaging from that pack of insulation?

BAM has thought for a long time that this would have a significant impact, and has been working with WRAP and the UK Contractors Group to develop a set of conversion factors which reflect the impact of the waste removed from our construction sites. These have just been released on the WRAP and Zero Waste Scotland websites.

These conversion factors not only include the carbon impact of the transport removing the waste from site (which is all the current DEFRA factors include), but also the impact of treating the waste (e.g. from recycling, incineration with energy recovery or sending it to landfill). For construction waste, they also include the embodied carbon in making the material in the first place. This is an important factor that hasn’t been given much thought before but we believe this is vital to understand and then reduce the total impact that our buildings have.

Using the new factors, we’ve calculated the carbon impact of the waste removed from our construction sites during 2013, and although we expected the impact to be significant, we didn’t realise how substantial it would be. The final figure for all construction, demolition and excavation waste removed from our sites was a staggering 35,000 tonnes CO2e (about double our company carbon footprint for 2013). Almost 30,000 tonnes of this is due to the embodied carbon in materials, which is the key part the industry has been missing till now.

Key waste streams contributing to this included mixed packaging and plastics at 3,500 tonnes (10%), as well as our mixed construction waste at 22,000 tonnes (63%). Although soils and stones are by far our biggest waste stream, making up over 70% of all waste, it only accounts for just over 1% of carbon emissions.

At BAM, we’ve reduced waste intensity by 37% since 2008, which using our new factors, amounts to a saving of around 20,000 tonnes of CO2e. To reduce this impact further we must focus on the circular economy principles, as highlighted in our previous blog posts, and ensure as contractors, designers and clients that we collaborate to:

Design for re-use and recovery, especially reuse of packaging materials

Design for off-site construction

Design for materials optimisation

Design for waste efficient procurement

Design for flexibility and deconstruction

We and the wider sector have already made great progress in reducing waste but there is still more to do to reduce embodied carbon.